1. Field of the Invention
This invention relates to weighing devices and is more particularly directed to precision cut-off weighing apparatus combined with a weighing device.
2. Description of the Prior Art
With the advent of drawing blood from blood donors, Federal laws were passed limiting the amount of blood that can be drawn from individuals at any one time, and also the frequency of such blood donations. It became necessary to provide weighing devices that would cut-off the flow of blood as soon as the desired amount of blood was collected in a receptacle. However, these devices were either not accurate enough nor did they cut-off the flow of blood quickly and properly.
The present weighing device being used by most blood banks to assist in the collecting of a predetermined quantity of blood consists of a balance type scale on one side of which a weight is placed and on the other side a blood collecting bag is hung on a lever attached thereto. This type of device has been found not to be as accurate as required by the law. Also, if this scale is placed on a surface that is not level, a further error in weight will result. The present invention contemplates avoiding the above indicated objectsion of the present cut-off weighting devices.